The differentiation of bovine lens cells is accompanied with two fold enrichment of phenylalanine tRNA by the induction of a new isoaccepting tRNA Phe (tRNAl Phe) with no change in the abundance of the other isoacceptor, tRNA2 Phe. We recently determined the sequences of these two lens tRNA Phes. Our results showed that tRNA2 Phe is identical to beef liver tRNA Phe while tRNAl Phe differs from tRNA2 Phe by its primary sequence rather than post-transcriptional modification. The biological role of this new tRNA Phe remains to be studied. The objectives of this project are studies on (1) the codon specificity of these two tRNA Phes, (2) competitive efficiency of these two tRNA Phes during in vitro translation of synthetic and natural messengers and (3) the site specificity for the incorporation of phenylalanine residues in alpha-crystallin chain mediated by tRNAl Phe and tRNA2 Phe. We will also analyze the sequences of other lens "specialized" tRNAs.